A filter cartridge is typically constituted by a gastight housing that accommodates a cylindrical filter element having an inner passage and a gastight head that is integrally connected to the housing. In the case of a disposable type, the housing and the head are integrally connected to each other to form one filter cartridge as a whole. In the case of a replaceable type, the head is detachably connected to the housing by fastening means having seal means and the filter element is replaced before a filtration life limit.
Although usually there are a convoluted type filter element and a pleated type filter element, the latter filter element has become mainstream because of its large filtration area. As shown in FIG. 2, a pleated type filter element 10 is constituted by a filter medium 22, which is fabricated by folding in pleats a superimposed body that is obtained by attaching a pair of porous supporting sheets to both surfaces of a thermoplastic filtration film and by sealing both sides edges together, an inner cylinder 21 having a large number of apertures 24 and an outer cylinder 23 having a large number of apertures 25, which support the filter medium from both surfaces, and top and bottom covers, which are fusion bonded to the top and bottom ends of the filter medium 22 to hermetically seal the filter medium, (only the top cover 28 is shown in FIG. 2).
As shown in FIGS. 5 and 6, in a filter device comprising a housing 12 which is pivoted to a supporting frame 15 and a head 11 which is fixed to the supporting frame 15, an inlet for a liquid to be treated is usually provided in the lower part or head of the housing (in this example, in the head) and an outlet for a filtered liquid is usually provided in the lower part or head of the housing (in this example, in the head). Furthermore, in some cases, a gas vent port to vent gas bubbles generated from gases dissolved in a liquid to be treated or a filtered liquid may sometimes be provided in the head (in this example, this gas vent port is not used).
In FIG. 2, FIGS. 5 and 6, a liquid to be treated is introduced from an inlet for a liquid to be treated which is provided at the head 11 to between a filter element 10 and the housing 12, and the liquid to be treated permeates a filter medium 22 from the multi-aperture outer cylinder 23. Particles or solid contamination are trapped to the outer surface of the filter medium 22, and the filtered liquid which has permeated the filter medium 22 flows from an inner passage of a multi-aperture inner cylinder 21 via an outlet leading for a filtered liquid 27 to a filtered liquid discharge outlet which is provided at the head 11. Incidentally, a stepped portion 26 which serves as a finger engaging portion during the extraction is formed in the outlet leading 27.
Filters each using a cartridge are classified into a type in which a cartridge to be used is integral with a housing portion and a type in which a cartridge is replaceable. The present invention provides a jig for replacing a filter element in a replaceable cartridge filter.